Hydraulic releases are employed to secure life rafts and the like to the deck of a ship during normal operation. Should the ship sink and the hydraulic devices thereby be exposed to increased pressure, they are designed to release at preset depths, e.g. between 5 and 25 feet, to allow the buoyant life rafts to return to the surface for the use of survivors.
Government agencies require that the hydraulic releases be periodically tested to ensure proper operation should an emergency arise.
According to prior techniques, hydraulic releases had been tested by submerging them in water which applied hydraulic pressure to the release. The pressure was provided either by a head of water or by use of a pressurized vessel. Such techniques, while accurately testing the operability of the hydraulic release, were objectionable from the point of view of cost and inconvenience of submergence under water and subsequent retrieval from the water.
According to my earlier invention, U.S. Pat. No. 4,018,079, for METHOD AND APPARATUS FOR TESTNG HYDRAULIC RELEASES, this testing may be performed in a superatmospheric pressure vessel using air, instead of water, as the pressure medium, thus to avoid the messiness, time consumption and added cost of water testing, while using a medium of increased permeability to defect emerging problems not readily apparent with water testing.
A further testing service condition requirement imposed by the government agencies is that the release apparatus be tested under a known tension, e.g. 200-3750 pounds, designated to approximate the tension that a hydraulic release would be subjected to should a vessel actually submerge, due, e.g., to the buoyancy of the life raft or other unforeseen stresses accompanying the sinking.
In my earlier invention, this tensioning was determined by the manufacturer's marking (62, FIG. 5) on the shaft (64) connected to the spring (60) of the hydraulic release. In another method shown in Katz, U.S. Pat. No. 4,217,772, the tension is measured by means of a dynamometer which is then isolated from the system and removed before the hydraulic release is placed into the pressure vessel for actual release testing. Neither of these approaches is wholly satisfactory.
It is an objective of my invention to provide an improved apparatus and method for the testing of hydraulic releases.